SMTP
protocol for sending e-mails
Definition: What is an SMTP server?
The SMTP protocol was defined in 1982 by RFC 821. SMTP enables e-mail to be sent over the Internet, and is used to communicate on port TCP/25 between MTA (Mail Transfer Agent) services.
It is one of the oldest Internet protocols, and has always been backward-compatible. The protocol has undergone a few slight changes, with RFC 2821 and the ability to handle attachments via the MIME protocol (RFC 2045 to 2049), but the basis and its primary foundation have remained unchanged. SMTP is a fairly simple protocol, which could almost be reduced to the use of 4 commands: HELO, MAIL FROM, RCPT TO, DATA.
Example of an SMTP transaction with a mail server
z03:~# telnet a.mx.mail.yahoo.com 25
220 mta604.mail.mud.yahoo.com ESMTP YSmtp service ready
helo toto.com
250 mta604.mail.mud.yahoo.com
mail from: <toto@toto.com>
250 sender <totot@toto.com> ok
rcpt to: <xxxxxx@yahoo.com>
250 recipient <xxxxxx@yahoo.com> ok
data
354 go ahead
Subject: Test
Test
.
250 ok dirdel
quit
221 mta604.mail.mud.yahoo.com
Learn about HORNETSECURITY’S SERVICES
Interested in Related Topics?
Did you like our contribution to SMPT? Then other articles in our knowledge base might interest you as well! We help you learn more about cybersecurity related topics such as Emotet, Trojans, IT Security, Cryptolocker Ransomware, Phishing, GoBD, Cyber Kill Chain and Computer Worms.